The great helmet or pot helmet was developed around the 12th century during the time of the crusades and it was used until the 14th century by both knights and heavy European infantrymen. In these centuries it changed from a simple design with only narrow slits for the eyes and mouth to a rounded helmet.

The grreat helmet provided more protection than the earlier nasal helmet but it reduced the peripheral vision and it had limited ventilation so generally it was put on just before the battle. A smaller helmet like the secret or the bascinet was often worn underneath the great helmet.